The present application claims priority under 35 U.S.C. xc2xa7 119 of German Patent Application No. 199 13 929.6, filed on Mar. 26, 1999, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a device for determining the properties of a material web, e.g., a paper web, having at least one radiation source and at least one identification device for radiation that is emitted by the radiation source and that penetrates the material web and/or is reflected by the material web.
2. Discussion of Background Information
Devices of the type generally disclosed above are known, e.g., from U.S. Pat. No. 5,233,195, which describes the use of a xcex2-emitter and an X ray source, as well as an ionization chamber as a detection device. Known from U.S. Pat. No. 5,010,766 is a plate divided into four sections, which is provided on one side of a moving web that is being examined. The plate interacts with a configuration of four eddy current sensors on the other side of the web. In the article (ISBN 952-5183-09-2) xe2x80x9cPaper Machine Applications with Fullsheet Imaging Measurementxe2x80x9d by Shih-Chin Chen et al., pages 330-337, Control Systems ""98, xe2x80x9cInformation Tools to Match the Evolving Operator Role,xe2x80x9d Sep. 1-3, 1998, Porvoo, Finland, a configuration comprising a light source, CCD cameras, and high speed processors is mentioned, where the light from the light source transmitted by a moving web is detected by CCD cameras.
The present invention provides an apparatus and a process which permit examination of a material web with a high degree of accuracy, particularly with respect to a number of different properties of the material web.
According to an exemplary embodiment of the invention, the detection device includes at least one detection area that is divided in non-uniform fashion into a large number of individual sensors.
The division of the detection area of the detection device permits examination of the material web that is both locally and temporally differentiated, because part of the radiation that strikes one of the individual sensors is characteristic of an area of the material web that was either penetrated or reflected by the given radiation. With a rapid read-out of the individual sensors belonging to the detection device, momentary pictures of the material web with respect to the properties under examination can be prepared in rapid sequence which, in principle, permits a seamless examination of the material web. The local resolution achievable with the invention is limited only by the size of the individual sensors. In principle, therefore, any desired level can be selected.
The non-uniform division of the detection area provided by the invention allows for an advantageous adjustment of the detection device to the conditions characteristic of the given measurement. In a particular embodiment, the movement of the material web relative to the detection device can be taken into account by the length of the individual detection areas of at least several of the individual sensors in the travel direction of the material web exceeding the length extending in the direction cross-wise thereto. In general, the individual sensors forming the detection area can differ with respect to the size and/or the shape of their individual detection areas.
According to another exemplary embodiment of the invention, it is also possible to vary the number of individual sensors per surface unit over the detection area. For example, it can be arranged in such a way that the number of individual sensors per surface unit in a central zone of the detection area is greater than in at least one marginal zone of the detection area. An optimal relation can be achieved thereby between the signal/noise ratio and the total number of sensors.
In another particular embodiment of the invention, the individual sensors can be microprocessors which, e.g., have individual detection areas of less than approximately 1 cm2, preferably of about 1 mm2.
In another embodiment of the invention, a 10xc3x9710 (or 100 total) array of microsensors, each with a square detection area of approximately 1 mm2, can be positioned in checkerboard pattern. In this manner, the microsensors can form a continuous, square detection zone that may be positioned in a center of a detection area. The detection area can also include marginal zones formed, e.g., of oblong, particularly rectangular, microsensors having individual detection areas of several mm2 and having longitudinal axes oriented in the web travel direction.
It is noted that it is fundamentally possible to utilize any desired geometric arrangement of the individual sensors. For example, the detection areas, at least in certain zones, can be provided in the form of concentrically positioned, ring-shaped individual sensors. Further, the given detection zone, or the entire detection area, can be, e.g., rectangular, circular, or triangular.
Furthermore, the detection area according to the invention can include a plurality of detection zones formed of individual sensors which are, e.g., staggered or offset relative to one another or which can be movably positioned.
In another embodiment of the invention, the microsensors can be semiconductor detectors, e.g., semiconductor sensors of very pure silicon manufactured especially for detecting electromagnetic radiation or electrically charged particles. In principle, it is also possible to use other radiation detectors, e.g., ionization detectors (such as ionization chambers) or scintillation detectors (such as scintillation tubes).
In principle, the device according to the invention can be provided with an approximately point-like radiation source that emits radiation in a specific solid-angular area. The radiation emitted by a point radiation source can also be widened by additional devices to permit planar radiation of the material web. It may be preferable for the radiation source to be designed in such a way that a radiation surface is provided. Further, the shape of the radiation area of the radiation source may preferably correspond to that of the detection area of the detection device.
It is also possible to provide a plurality of individual radiation sources instead of a single radiation source and to arrange those sources in the form of a source array.
It may be preferable for the radiation source, in keeping with the above-noted features of the invention, to be designed to provide a substantially homogeneous or uniform distribution of radiation intensity when no material is located in the radiation path.
The radiation source can be designed to release radiation with a constant intensity over time or with an intensity that is preferably varied in regular fashion, specifically a pulsing intensity. The radiation used can be of an electromagnetic type, particularly that provided by microwaves, LED light, laser beams, or X rays. In cases in which pulsed radiation is used, LEDs or lasers are the preferred radiation source. The given radiation source can be designed so as to permit adjustment of the wavelength of the electromagnetic radiation. It is also possible to use radiation sources with different wavelengths simultaneously. In principle, it is also possible to combine sources using different types of radiation.
In another possible embodiment of the invention, the radiation source is designed to radiate electrically charged particles and is particularly designed as an xcex1-emitter and/or a xcex2-emitter.
During operation of the device according to the invention, it may be preferable to position the radiation source on one side of the material web and the detection device on the other side, so that radiation penetrating the material web will be recorded. In principle, it is also possible to position the radiation source and the detection device on the same side of the material web and to detect the radiation reflected from the material web. Moreover, transmission and reflection measurements can be combined such that both radiation penetrating the material web and radiation reflected by the material web are detected, e.g., in conjunction with axial sensors.
Especially in conjunction with electromagnetic radiation, it is possible for at least one component assigned to the radiation source or the detection device to be positioned in the diffusion path of the radiation source, such that the component will modify at least one property of the radiation. This kind of component might be, e.g., a diffraction grid, which is positioned either close to the detection device or close to the radiation source. The spectral analysis of emitted radiation from this kind of grid can be used in a traversing measurement in which the device according to the invention is moved cross-wise to the material web travel direction to examine the properties of the material web which are dependent on the wavelength of the radiation interacting with the material web. It is also possible to install, e.g., a polarization filter in the radiation path of the device, according to the invention.
The radiation source and/or the detection device can, e.g., be positioned substantially cross-wise to the material web travel direction in swiveling or movable fashion, in order to execute any desired relative motion between the device according to the invention and a moving material web.
The present invention is also directed to a process in which at least one device of the type described above is utilized to determine the properties of a material web, e.g., a paper web.
In a particular embodiment of the process, the signals delivered by the individual sensors can be evaluated independently of one another. Thus, each individual sensor can deliver a measurement for a specific area of the material web. In this manner, comparatively large-scale momentary pictures of the material web can be compiled which permit precise examination of a local distribution of a property or properties of the material web to be performed.
According to another embodiment of the invention, the signals of at least one group of individual sensors, preferably forming a continuous detection zone in the detection area, may be compiled and, in particular, can be employed to form a mean value.
It is possible to considerably enhance the accuracy of the measured values which can be obtained with this kind of compilation by providing a large number of individual sensors per detection area. As an alternative to the formation of a mean value, or in addition thereto, the signal-to-noise ratio can be improved, and the measuring accuracy thus increased, by applying complex filtering algorithms (e.g., locally distributed Kalman filters). In this regard, the improvement is proportional, at least in theory, to 1/{square root over (n)}, where n is the number of the individual sensors included in the given instance of signal processing.
According to another exemplary embodiment of the process according to the invention, it is possible to swivel or move the radiation source and/or the detection device as a function of the speed of the moving material web.
In this regard, it is possible to achieve a maximum degree of local and temporal resolution, or measuring accuracy, with a minimum number of individual sensors, particularly when the detection area is subdivided according to the web speed and the swiveling or traversing speed, as well as the size, form, and orientation of the individual sensors.
A particular application of the device or process according to the invention includes determining the basis weight of the material web. Due to the good temporal and spatial resolution that can be achieved with the invention by providing a large number of individual sensors that form an unevenly distributed detection area, the invention makes it simultaneously possible to determine the microformation of the material web when the individual sensors are appropriately small.
The invention also makes it possible to identify the border of the material web and thus to determine the exact location of the lateral edges of the material web.
The present invention is directed to an apparatus for determining the properties of a material web that includes at least one radiation source, and at least one detection device adapted to detect radiation emitted from the at least one radiation source that at least one of penetrates and is reflected by the material web. The detection device can include at least one detection area unevenly divided into a plurality of individual sensors. Further, the material web can be a paper web.
According to a feature of the instant invention, individual detection areas of the plurality of individual sensors can differ with respect to at least one of size and form.
In accordance with another feature of the invention, a number of the plurality of individual sensors per surface unit may vary over the at least one detection area. Further, the number of individual sensors per surface unit may be larger in a central zone of the detection area than in at least one rim zone of the detection area.
According to an aspect of the present invention, the detection area can include a plurality of detection zones formed in differing fashion by the plurality of individual sensors. The detection zones may be arranged in one of an offset and staggered fashion relative to one another.
In accordance with another aspect of the instant invention, the detection area can include at least two detection zones in which structurally equivalent ones of the plurality of individual sensors are combined. The structurally equivalent ones of the plurality of individual sensors can have at least one of common sizes and forms of individual detection areas of the individual sensors.
In accordance with a further feature of the invention, individual detection areas of at least some of the plurality of individual sensors may be oblong in form. The oblong form can be one of rectangular and trapezoidal.
According to still another feature of the invention, individual detection areas of at least several of the plurality of individual sensors may extend further in a web travel direction than in a direction cross-wise to the web travel direction.
Further, the detection area can include a plurality of zones, and the detection area, in at least one of the plurality of zones, may be arranged as a single-row of individual sensors.
At least several of the plurality of individual sensors can include microsensors. The microsensors can have an individual detection area of less than approximately 1 cm2. Further, the microsensors can have individual detection area of less than several mm2. The microsensors can also have an individual detection area of less than approximately 1 mm2.
In accordance with a further aspect of the instant invention, the detection area can include a plurality of zones, and the detection area, in at least one of the plurality of zones, can include concentrically arranged, ring-shaped individual sensors.
According to a still further feature of the invention, the detection area can be one of approximately rectangular, circular, and triangular.
According to still another feature of the present invention, the plurality of individual sensors may include semiconductor detectors.
The plurality of individual sensors may include at least one of ionization detectors and scintillation detectors. The ionization detectors can include ionization chambers and the scintillation detectors can include scintillation tubes.
Moreover, the at least one radiation source can include a radiating surface and the radiating surface can be structured to at least approximately correspond to the at least one detection area.
Further, the at least one radiation source can include a plurality of individual radiation sources arranged as a source array.
The at least one radiation source can be adapted to provide a homogeneous distribution of radiation intensity onto the at least one detection area.
Another feature of the present invention is that at least one radiation source can be adapted to release radiation with at least one of a constant intensity over time and a regularly varying intensity. The regularly varying intensity can include a pulsing intensity.
Still another feature of the instant invention is that the at least one radiation source can be adapted to radiate at least one of electromagnetic radiation, LED light, laser beams, and X rays. The electromagnetic radiation may include microwaves.
In a further feature of the present invention, the at least one radiation source can be adapted to radiate electrically charged particles. The at least one radiation source may include at least one of an xcex1-emitter and/or a xcex2-emitter.
A still further feature of the invention can include at least one component assigned to one of the at least one radiation source and the at least one detection device, and the at least one component being positionable in a diffusion path of the at least one radiation source. In this manner, at least one property of the radiation can be modified. The at least one component can be an optical component, and the optical component can include a diffraction grid or polarization filter.
According to another aspect of the invention, at least one of the at least one radiation source and the at least one detection device may be one of swivelable and movable. The at least one of the at least one radiation source and the at least one detection device can be one of swivelable and movable substantially cross-wise to a web travel direction.
The present invention is directed to a process for determining the properties of a material web with at least one apparatus that include at least one radiation source and at least one detection device including at least one detection area unevenly divided into a plurality of individual sensors. The process can include directing radiation from the at least one radiation source toward the material web, and detecting, on the unevenly divided plurality of individual sensors, the emitted radiation from the at least one radiation source which at least one of penetrates and is reflected by the material web.
According to a feature of the invention, the process can further include determining a profile of at least one property of the material web. The profile of the at least one property can be determined at least one of substantially in and cross-wise to a web travel direction.
In accordance with another feature of the present invention, the process may further include obtaining a two-dimensional picture of the material web with respect to at least one property of the material web to be determined.
A further feature of the invention can include modifying at least one property of the radiation by at least one component positioned in a diffusion path of the radiation.
Still another feature of the present invention can include modifying at least one property of the radiation in accordance with at least one of a direction and a speed of at least one of the at least one radiation source and the at least one detection device relative to the material web.
The process can also include reading out data from the individual sensors in one of a parallel and sequential fashion at high speed. The individual sensors can include a CCD camera.
According to still another feature of the present invention, signals delivered by the individual sensors may be evaluated independently of one another.
The signals of at least one group of the individual sensors which are arranged to form a continuous detection zone in the detection area may be compiled and utilized to form a mean value.
In accordance with a further feature of the instant invention, a basis weight of the material web may be determined.
According to a still further feature of the present invention, formation of the material web may be determined. Further, microformation of the material web can be determined.
In accordance with still another feature of the invention, the material web includes lateral edges, and a position of at least one of the lateral edges of the material web can be determined.
According to another feature of the instant invention, at least one of the at least one radiation source and the at least one detection device can be one of swivelable and movable dependent upon a speed of the moving material web.
The present invention is directed to an apparatus for determining the properties of a material web that includes at least one radiation source and at least one detection device adapted to detect radiation emitted from the at least one radiation source that at least one of penetrates and is reflected by the material web. The detection device includes at least one detection area non-uniformly divided into a plurality of individual sensors, such that some of the plurality of individual sensors are arranged to extend further in a web travel direction than in a direction cross-wise to the web travel direction.
In accordance with yet another feature of the present invention, the detection area can include a plurality of zones, and, in at least one of the plurality of zones, the some of the plurality of individual sensors arranged to extend further in the web travel direction than in the direction cross-wise to the travel direction are arranged as a single-row of individual sensors. Further, in at least another of the plurality of zones, others of the plurality of individual sensor are substantially square shaped and arranged in a checkerboard fashion.